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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Licensed to the Apache Software Foundation (ASF) under one<a name="line.2"></a>
<span class="sourceLineNo">003</span> * or more contributor license agreements. See the NOTICE file<a name="line.3"></a>
<span class="sourceLineNo">004</span> * distributed with this work for additional information<a name="line.4"></a>
<span class="sourceLineNo">005</span> * regarding copyright ownership. The ASF licenses this file<a name="line.5"></a>
<span class="sourceLineNo">006</span> * to you under the Apache License, Version 2.0 (the<a name="line.6"></a>
<span class="sourceLineNo">007</span> * "License"); you may not use this file except in compliance<a name="line.7"></a>
<span class="sourceLineNo">008</span> * with the License. You may obtain a copy of the License at<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.10"></a>
<span class="sourceLineNo">011</span> *<a name="line.11"></a>
<span class="sourceLineNo">012</span> * Unless required by applicable law or agreed to in writing, software<a name="line.12"></a>
<span class="sourceLineNo">013</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.13"></a>
<span class="sourceLineNo">014</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.14"></a>
<span class="sourceLineNo">015</span> * See the License for the specific language governing permissions and<a name="line.15"></a>
<span class="sourceLineNo">016</span> * limitations under the License.<a name="line.16"></a>
<span class="sourceLineNo">017</span> */<a name="line.17"></a>
<span class="sourceLineNo">018</span>package org.apache.hadoop.hbase.zookeeper;<a name="line.18"></a>
<span class="sourceLineNo">019</span><a name="line.19"></a>
<span class="sourceLineNo">020</span>import java.util.concurrent.atomic.AtomicBoolean;<a name="line.20"></a>
<span class="sourceLineNo">021</span>import org.apache.hadoop.hbase.Stoppable;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import org.apache.hadoop.hbase.util.Bytes;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import org.apache.zookeeper.KeeperException;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import org.slf4j.Logger;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import org.slf4j.LoggerFactory;<a name="line.26"></a>
<span class="sourceLineNo">027</span><a name="line.27"></a>
<span class="sourceLineNo">028</span>/**<a name="line.28"></a>
<span class="sourceLineNo">029</span> * Handles coordination of a single "leader" instance among many possible candidates. The first<a name="line.29"></a>
<span class="sourceLineNo">030</span> * {@link ZKLeaderManager} to successfully create the given znode becomes the leader, allowing the<a name="line.30"></a>
<span class="sourceLineNo">031</span> * instance to continue with whatever processing must be protected. Other {@link ZKLeaderManager}<a name="line.31"></a>
<span class="sourceLineNo">032</span> * instances will wait to be notified of changes to the leader znode. If the current master instance<a name="line.32"></a>
<span class="sourceLineNo">033</span> * fails, the ephemeral leader znode will be removed, and all waiting instances will be notified,<a name="line.33"></a>
<span class="sourceLineNo">034</span> * with the race to claim the leader znode beginning all over again.<a name="line.34"></a>
<span class="sourceLineNo">035</span> * @deprecated Not used<a name="line.35"></a>
<span class="sourceLineNo">036</span> */<a name="line.36"></a>
<span class="sourceLineNo">037</span>@Deprecated<a name="line.37"></a>
<span class="sourceLineNo">038</span>@InterfaceAudience.Private<a name="line.38"></a>
<span class="sourceLineNo">039</span>public class ZKLeaderManager extends ZKListener {<a name="line.39"></a>
<span class="sourceLineNo">040</span> private static final Logger LOG = LoggerFactory.getLogger(ZKLeaderManager.class);<a name="line.40"></a>
<span class="sourceLineNo">041</span><a name="line.41"></a>
<span class="sourceLineNo">042</span> private final Object lock = new Object();<a name="line.42"></a>
<span class="sourceLineNo">043</span> private final AtomicBoolean leaderExists = new AtomicBoolean();<a name="line.43"></a>
<span class="sourceLineNo">044</span> private final String leaderZNode;<a name="line.44"></a>
<span class="sourceLineNo">045</span> private final byte[] nodeId;<a name="line.45"></a>
<span class="sourceLineNo">046</span> private final Stoppable candidate;<a name="line.46"></a>
<span class="sourceLineNo">047</span><a name="line.47"></a>
<span class="sourceLineNo">048</span> public ZKLeaderManager(ZKWatcher watcher, String leaderZNode, byte[] identifier,<a name="line.48"></a>
<span class="sourceLineNo">049</span> Stoppable candidate) {<a name="line.49"></a>
<span class="sourceLineNo">050</span> super(watcher);<a name="line.50"></a>
<span class="sourceLineNo">051</span> this.leaderZNode = leaderZNode;<a name="line.51"></a>
<span class="sourceLineNo">052</span> this.nodeId = identifier;<a name="line.52"></a>
<span class="sourceLineNo">053</span> this.candidate = candidate;<a name="line.53"></a>
<span class="sourceLineNo">054</span> }<a name="line.54"></a>
<span class="sourceLineNo">055</span><a name="line.55"></a>
<span class="sourceLineNo">056</span> public void start() {<a name="line.56"></a>
<span class="sourceLineNo">057</span> try {<a name="line.57"></a>
<span class="sourceLineNo">058</span> watcher.registerListener(this);<a name="line.58"></a>
<span class="sourceLineNo">059</span> String parent = ZKUtil.getParent(leaderZNode);<a name="line.59"></a>
<span class="sourceLineNo">060</span> if (ZKUtil.checkExists(watcher, parent) &lt; 0) {<a name="line.60"></a>
<span class="sourceLineNo">061</span> ZKUtil.createWithParents(watcher, parent);<a name="line.61"></a>
<span class="sourceLineNo">062</span> }<a name="line.62"></a>
<span class="sourceLineNo">063</span> } catch (KeeperException ke) {<a name="line.63"></a>
<span class="sourceLineNo">064</span> watcher.abort("Unhandled zk exception when starting", ke);<a name="line.64"></a>
<span class="sourceLineNo">065</span> candidate.stop("Unhandled zk exception starting up: " + ke.getMessage());<a name="line.65"></a>
<span class="sourceLineNo">066</span> }<a name="line.66"></a>
<span class="sourceLineNo">067</span> }<a name="line.67"></a>
<span class="sourceLineNo">068</span><a name="line.68"></a>
<span class="sourceLineNo">069</span> @Override<a name="line.69"></a>
<span class="sourceLineNo">070</span> public void nodeCreated(String path) {<a name="line.70"></a>
<span class="sourceLineNo">071</span> if (leaderZNode.equals(path) &amp;&amp; !candidate.isStopped()) {<a name="line.71"></a>
<span class="sourceLineNo">072</span> handleLeaderChange();<a name="line.72"></a>
<span class="sourceLineNo">073</span> }<a name="line.73"></a>
<span class="sourceLineNo">074</span> }<a name="line.74"></a>
<span class="sourceLineNo">075</span><a name="line.75"></a>
<span class="sourceLineNo">076</span> @Override<a name="line.76"></a>
<span class="sourceLineNo">077</span> public void nodeDeleted(String path) {<a name="line.77"></a>
<span class="sourceLineNo">078</span> if (leaderZNode.equals(path) &amp;&amp; !candidate.isStopped()) {<a name="line.78"></a>
<span class="sourceLineNo">079</span> handleLeaderChange();<a name="line.79"></a>
<span class="sourceLineNo">080</span> }<a name="line.80"></a>
<span class="sourceLineNo">081</span> }<a name="line.81"></a>
<span class="sourceLineNo">082</span><a name="line.82"></a>
<span class="sourceLineNo">083</span> private void handleLeaderChange() {<a name="line.83"></a>
<span class="sourceLineNo">084</span> try {<a name="line.84"></a>
<span class="sourceLineNo">085</span> synchronized (lock) {<a name="line.85"></a>
<span class="sourceLineNo">086</span> if (ZKUtil.watchAndCheckExists(watcher, leaderZNode)) {<a name="line.86"></a>
<span class="sourceLineNo">087</span> LOG.info("Found new leader for znode: {}", leaderZNode);<a name="line.87"></a>
<span class="sourceLineNo">088</span> leaderExists.set(true);<a name="line.88"></a>
<span class="sourceLineNo">089</span> } else {<a name="line.89"></a>
<span class="sourceLineNo">090</span> LOG.info("Leader change, but no new leader found");<a name="line.90"></a>
<span class="sourceLineNo">091</span> leaderExists.set(false);<a name="line.91"></a>
<span class="sourceLineNo">092</span> lock.notifyAll();<a name="line.92"></a>
<span class="sourceLineNo">093</span> }<a name="line.93"></a>
<span class="sourceLineNo">094</span> }<a name="line.94"></a>
<span class="sourceLineNo">095</span> } catch (KeeperException ke) {<a name="line.95"></a>
<span class="sourceLineNo">096</span> watcher.abort("ZooKeeper error checking for leader znode", ke);<a name="line.96"></a>
<span class="sourceLineNo">097</span> candidate.stop("ZooKeeper error checking for leader: " + ke.getMessage());<a name="line.97"></a>
<span class="sourceLineNo">098</span> }<a name="line.98"></a>
<span class="sourceLineNo">099</span> }<a name="line.99"></a>
<span class="sourceLineNo">100</span><a name="line.100"></a>
<span class="sourceLineNo">101</span> /**<a name="line.101"></a>
<span class="sourceLineNo">102</span> * Blocks until this instance has claimed the leader ZNode in ZooKeeper<a name="line.102"></a>
<span class="sourceLineNo">103</span> */<a name="line.103"></a>
<span class="sourceLineNo">104</span> public void waitToBecomeLeader() {<a name="line.104"></a>
<span class="sourceLineNo">105</span> while (!candidate.isStopped()) {<a name="line.105"></a>
<span class="sourceLineNo">106</span> try {<a name="line.106"></a>
<span class="sourceLineNo">107</span> if (ZKUtil.createEphemeralNodeAndWatch(watcher, leaderZNode, nodeId)) {<a name="line.107"></a>
<span class="sourceLineNo">108</span> // claimed the leader znode<a name="line.108"></a>
<span class="sourceLineNo">109</span> leaderExists.set(true);<a name="line.109"></a>
<span class="sourceLineNo">110</span> if (LOG.isDebugEnabled()) {<a name="line.110"></a>
<span class="sourceLineNo">111</span> LOG.debug("Claimed the leader znode as '" + Bytes.toStringBinary(nodeId) + "'");<a name="line.111"></a>
<span class="sourceLineNo">112</span> }<a name="line.112"></a>
<span class="sourceLineNo">113</span> return;<a name="line.113"></a>
<span class="sourceLineNo">114</span> }<a name="line.114"></a>
<span class="sourceLineNo">115</span><a name="line.115"></a>
<span class="sourceLineNo">116</span> // if claiming the node failed, there should be another existing node<a name="line.116"></a>
<span class="sourceLineNo">117</span> byte[] currentId = ZKUtil.getDataAndWatch(watcher, leaderZNode);<a name="line.117"></a>
<span class="sourceLineNo">118</span> if (currentId != null &amp;&amp; Bytes.equals(currentId, nodeId)) {<a name="line.118"></a>
<span class="sourceLineNo">119</span> // claimed with our ID, but we didn't grab it, possibly restarted?<a name="line.119"></a>
<span class="sourceLineNo">120</span> LOG.info(<a name="line.120"></a>
<span class="sourceLineNo">121</span> "Found existing leader with our ID (" + Bytes.toStringBinary(nodeId) + "), removing");<a name="line.121"></a>
<span class="sourceLineNo">122</span> ZKUtil.deleteNode(watcher, leaderZNode);<a name="line.122"></a>
<span class="sourceLineNo">123</span> leaderExists.set(false);<a name="line.123"></a>
<span class="sourceLineNo">124</span> } else {<a name="line.124"></a>
<span class="sourceLineNo">125</span> LOG.info("Found existing leader with ID: {}", Bytes.toStringBinary(currentId));<a name="line.125"></a>
<span class="sourceLineNo">126</span> leaderExists.set(true);<a name="line.126"></a>
<span class="sourceLineNo">127</span> }<a name="line.127"></a>
<span class="sourceLineNo">128</span> } catch (KeeperException ke) {<a name="line.128"></a>
<span class="sourceLineNo">129</span> watcher.abort("Unexpected error from ZK, stopping candidate", ke);<a name="line.129"></a>
<span class="sourceLineNo">130</span> candidate.stop("Unexpected error from ZK: " + ke.getMessage());<a name="line.130"></a>
<span class="sourceLineNo">131</span> return;<a name="line.131"></a>
<span class="sourceLineNo">132</span> }<a name="line.132"></a>
<span class="sourceLineNo">133</span><a name="line.133"></a>
<span class="sourceLineNo">134</span> // wait for next chance<a name="line.134"></a>
<span class="sourceLineNo">135</span> synchronized (lock) {<a name="line.135"></a>
<span class="sourceLineNo">136</span> while (leaderExists.get() &amp;&amp; !candidate.isStopped()) {<a name="line.136"></a>
<span class="sourceLineNo">137</span> try {<a name="line.137"></a>
<span class="sourceLineNo">138</span> lock.wait();<a name="line.138"></a>
<span class="sourceLineNo">139</span> } catch (InterruptedException ie) {<a name="line.139"></a>
<span class="sourceLineNo">140</span> LOG.debug("Interrupted waiting on leader", ie);<a name="line.140"></a>
<span class="sourceLineNo">141</span> }<a name="line.141"></a>
<span class="sourceLineNo">142</span> }<a name="line.142"></a>
<span class="sourceLineNo">143</span> }<a name="line.143"></a>
<span class="sourceLineNo">144</span> }<a name="line.144"></a>
<span class="sourceLineNo">145</span> }<a name="line.145"></a>
<span class="sourceLineNo">146</span><a name="line.146"></a>
<span class="sourceLineNo">147</span> /**<a name="line.147"></a>
<span class="sourceLineNo">148</span> * Removes the leader znode, if it is currently claimed by this instance.<a name="line.148"></a>
<span class="sourceLineNo">149</span> */<a name="line.149"></a>
<span class="sourceLineNo">150</span> public void stepDownAsLeader() {<a name="line.150"></a>
<span class="sourceLineNo">151</span> try {<a name="line.151"></a>
<span class="sourceLineNo">152</span> synchronized (lock) {<a name="line.152"></a>
<span class="sourceLineNo">153</span> if (!leaderExists.get()) {<a name="line.153"></a>
<span class="sourceLineNo">154</span> return;<a name="line.154"></a>
<span class="sourceLineNo">155</span> }<a name="line.155"></a>
<span class="sourceLineNo">156</span> byte[] leaderId = ZKUtil.getData(watcher, leaderZNode);<a name="line.156"></a>
<span class="sourceLineNo">157</span> if (leaderId != null &amp;&amp; Bytes.equals(nodeId, leaderId)) {<a name="line.157"></a>
<span class="sourceLineNo">158</span> LOG.info("Stepping down as leader");<a name="line.158"></a>
<span class="sourceLineNo">159</span> ZKUtil.deleteNodeFailSilent(watcher, leaderZNode);<a name="line.159"></a>
<span class="sourceLineNo">160</span> leaderExists.set(false);<a name="line.160"></a>
<span class="sourceLineNo">161</span> } else {<a name="line.161"></a>
<span class="sourceLineNo">162</span> LOG.info("Not current leader, no need to step down");<a name="line.162"></a>
<span class="sourceLineNo">163</span> }<a name="line.163"></a>
<span class="sourceLineNo">164</span> }<a name="line.164"></a>
<span class="sourceLineNo">165</span> } catch (KeeperException ke) {<a name="line.165"></a>
<span class="sourceLineNo">166</span> watcher.abort("Unhandled zookeeper exception removing leader node", ke);<a name="line.166"></a>
<span class="sourceLineNo">167</span> candidate.stop("Unhandled zookeeper exception removing leader node: " + ke.getMessage());<a name="line.167"></a>
<span class="sourceLineNo">168</span> } catch (InterruptedException e) {<a name="line.168"></a>
<span class="sourceLineNo">169</span> watcher.abort("Unhandled zookeeper exception removing leader node", e);<a name="line.169"></a>
<span class="sourceLineNo">170</span> candidate.stop("Unhandled zookeeper exception removing leader node: " + e.getMessage());<a name="line.170"></a>
<span class="sourceLineNo">171</span> }<a name="line.171"></a>
<span class="sourceLineNo">172</span> }<a name="line.172"></a>
<span class="sourceLineNo">173</span><a name="line.173"></a>
<span class="sourceLineNo">174</span> public boolean hasLeader() {<a name="line.174"></a>
<span class="sourceLineNo">175</span> return leaderExists.get();<a name="line.175"></a>
<span class="sourceLineNo">176</span> }<a name="line.176"></a>
<span class="sourceLineNo">177</span>}<a name="line.177"></a>
</pre>
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